When the device is switched to "sleep mode", the battery power is dropping rapidly, almost consume 1 percent battery power per 4/5 minutes. But after recovering from the mode, after a while, the power will recover some power.
It's weird!

Same happens to me. Before the update I charged my nook once a month or less, and it always was on sleep mode. Now it drains itself in two or three days not using it at all. I have to turn it off every night to avoid rapid drain. So far I found it without battery TWICE, and that never happened before. BTW, it's a Nook ST Glow